T3-Fertiliation and The First Two Weeks Flashcards
Phase 1 of fertilization
Penetration of Corona Radiata
In Phase 1 of fertilization, the movement of sperm tail allows what (2 things)
Sperm to pass freely through the Corona Radiata and for penetration of the follicular cells
Phase 2 of fertilization
Penetration of Zona Pellucida
Receptors on Zona Pellucida
ZP3 sperm receptors
Acrosome reaction
Triggered when ZP3 binding molecule on acrosomal membrane (sperm) binds with ZP3 on zona pellucida (egg)
Phase 3 of fertilization
Fusion of the sperm and oocyte cell membrane
IZUMO
egg binding protiens on inner acrosomal membrane of sperm cells
JUNO receptors
receptors on oocyte cell membranes
Sperm oocyte contact triggers what
cortical granules to release lysosomal enzymes aka the cortical reaction
The cortical reaction triggers
the zona reaction and shedding of JUNO receptors
Results of fertilization
Formation of female and male pronucleus
Formation of female pronuclus
secondary oocyte completes MD-II and the nucleus of the mature oocyte transforms into female pronucleus
Formation of male pronucleus
nucleus of sperm cell enlarges
Ootid
about 12hrs old and contains two pronuclei
When the chromosomes from the sperm and egg join the ootid is now called a what
zygote
Cleavage age
1 day old
Morula features
3 days old; 12-32 blastomeres
Mitotic divisions of the zygote produces this
blastomeres
Totipotent blastomere definition
has the ability to develop into both intra-embryonic and extra embryonic structures
When does compaction begin?
after the 8 cell stage between 3rd and 4th cleavage
What two structures does compaction result in?
Trophoblast (outer cell mass) and embryoblast (inner cell mass)
Features of Trophoblast (2)
Will contribute to extra-embryonic tissues such as the placenta but no contribution to the embryo
Features of embryoblast
Will form embryo proper, amniotic membrane, and the lining of the primative umbilical vessicle
Time when morula enters uterine cavitiy
about 4 days after fertilization
The blastocystic cavity forms when
fluid passes into the morula through the zona pellucida from the uterine cavity
Morula in uterine cavity is called
blastocyst
Establishing polarity
occurs when blastocystic cavity pushes the inner cell mass to one side
Between which days does the blastocyst hatch
4 and 6
Hatching is facillitated by what
proteolytic enzymes from the trophoblast which degenerate the Zona Pellucida
Dizygotic twins
two independently fertilized eggs
Monozygotic twins
one fertilized egg splits into two
Events of early blastocyst implantation occur between which days?
6 -10
Implantation into uterine wall: Events of day 6
blastocyst contacts uterine mucosa; blastocyst is said to be captured
Implantation into uterine wall: Events of day 7
formation of syncytiotrophoblast and cytotrophoblast
Implantation into the uterine wall: Events of day 8
errosion of maternal blood vessels and production of hCG by syncytiotrophoblast
Implantation into the uterine wall: Events of day 9
vacuoloes that appear in syncytium will fuse to form lacunae; lacunar stage of trophoblast development
Implantation Events of day 10
Blastocyst embeds deeper into uterine tissue; formation of closing plug in endometrial surface defect
Implantation into uterine wall Days 10 and 11
Adjacent lacunae fuse, forming lacunar networks filled with embryotroph
Embryotroph
Blood+glandular cell debris
Implantation into the uterine wall Days 11 and 12
Maternal blood from eroded endometrial BVs flows through lacunar networks; initiation of uroplacental circulation
Implantation into the uterine wall Days 12 and 13
Defect in endometrial endothelium is repaired
Day 21 (gestational age)
first contact with uterine wall occurs
Day 26 (gestational age)
fully implanted in uterine wall
Bilaminar Disc Formation Day 8
Embryoblast (inner cell mass) differentiates into Hypoblast Layer and Epiblast Layer
Hypoblast Layer
small cuboidal cells adjacent to the exocoelemic cavity
Epiblast Layer
tall columnar cells adjacent to the amniotic cavity
Exocoelemic cavity is aka what
Primary umbillical vessicle
Hypoblast+Exocoelomic membrane together line what?
Exocoelemic cavity
Epiblast+Amnion together line what?
amniotic cavity
Bilaminar Disc Formation Day 9
extraembryonic meosderm appears
Extraembryonic mesoderm does what?
surrounds the exocoelemic cavity/primary umbillical vessicle
Bilaminar Disc Formation Day 12
Cavities form within the extraembryonic mesoderm called the extraembryonic spaces
Bilaminar Disc Formation Day 13 (2 things)
Exrraembryonic coelomic spaces fuse creating the extraembryonic coelom (chorionic cavity) Primary umbillical vessicle begins to be pinched off creating the secondary umbillicle vessicle
Extraembryonic somatic mesoderm
adjacent to cytotrophoblast + covers amnion
Extraembryonic splanchnic mesoderm
covers secondary umbillicle vesicle
Extraembryonic coelom/chorionic cavity surrounds what?
the amnion and the exocoelomic cavity/umbillicle vessicle EXCEPT at the connecting stalk
Bilaminar disc= (2 things)
epiblast+hypoblast
Bilaminar disc formation Day 14 (2 things)
Larger part of primary vessicle may persist as as an exocoelomic cyst Hypoblast at the cranial end become tall columnar cells forminng the prechordal plate (site of future mouth)
Which day is this

Day 6
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Day 7
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Day 8
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Day 9
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Day 10
Which day is this?

Day 12
Migrating ___________ cells form the _____________ membrane
hypoblast; exocoelomic
Migrating ___________ cells separate and become _____________ forming the _____________
epiblast; amnioblasts; amnion